In JP Patent Application Publication No. 2008-126959 A, a technique is disclosed in which, if the tire pressure indicates a predetermined percentage decrease from a recommended air pressure, a warning lamp is turned on and lit in order to prompt or encourage the driver to travel with the recommended air pressure.
However, in the prior art technique, in a case in which a vehicle recommended air pressure is different between the front and rear wheels, when the driver has adjusted the tire pressure of each tire after a tire rotation, the warning lamp will be lit until a tire location is completed and the correspondence between each sensor unit and a wheel position will be updated. Thus, during this time, the driver will be given with a sense of discomfort.